The present invention relates to a storage control unit for controlling storage devices, such as magnetic disk devices, magnetic tape devices, optical disk devices, opt-magnetic disk devices, library devices and so on, so as to manage input/output (accesses) thereof to a host apparatus or device(s) of higher level, and in particular to a controller and a data storage system using thereof, in which fiber channels are used as routes or channels for accessing to such the storage devices.
In more detail, the present invention relates to a computer system, in which fiber channels standardized by ANSI X3T11 are applied as interfaces among the host computer(s), the storage devices such as the magnetic disk devices, and the storage control unit(s), and relates to a data storage system, in which a new storage control unit(s) is added to during an online operation of the computer system, thereby enabling to disperse or decentralize loads between or among the storage control units or to centralize functions which are conducted by plural controllers.
Conventionally, relating to install of an additional storage control unit(s), for example in Japanese Patent Laying-Open No. Hei 7-20994 (1995), there is described an enlargement in scale, especially, in a memory system of a large-scaled computer, by means of additional installations of a connecting adopter to the host computer in the memory system, a connecting adopter to the disk drive device and a shared cache memory, as well as function of inserting and extracting of live wires. And, there is proposed a manner wherein, the connecting adopter to the host computer, the connecting adopter to the disk drive unit and the shared cache memory mentioned above are installed one by one on an interior bus in the memory system.
The technology disclosed in Japanese Patent Laying-Open No. Hei 7-20994 (1995) adopts a shared cache memory method which is used generally in the memory system of the large-scaled computer, wherein each of the adopters connecting to the host computer(s) reads control information in a logical unit(s) located in the shared cache memory on the interior bus, sequentially, therefore it is able to access to a random logical unit without necessity of process of succession (i.e., taking over) or transfer of the control information of the logical unit between the connecting adopters to the host computer(s).
Also, relating multiplexing of the storage control units, each having the cache memory, for example in Japanese Patent Laying-Open No. Hei 7-160432 (1995), there is described a method, wherein the storage control unit is duplicated, while one of the storage control units is in a waiting condition as a standby storage control unit when occurring trouble in the other, thereby achieving redundancy of the storage control unit. Further, in Japanese Patent Laying-Open No. Hei 8-335144 (1996), there are also described the decentralization of loads by duplication of the storage control units and the redundancy of thereof when occurring problem therein.
In the technology in the above-mentioned Japanese Patent Laying-Open No. Hei 7-20994 (1995), however the control information of the logical unit is stored on the shared cache memory on the interior bus, therefore the enlargement of scale can be carried out only within a case or housing of one memory system.
In the technology in the above-mentioned Japanese Patent Laying-Open No. Hei 7-160432 (1995) or Hei 8-335144 (1996), however there is necessity that, in the storage control unit to be duplicated, each storage control unit must be connected physically in advance when being in a condition of off-line, and setting must be done on the logical unit which the each storage control unit takes in charge of, when operating under normal condition and when problem occurs therein. Further, the control information of the logical units are transferred by using the interior bus, therefore it depends on initial setting, and does not have expandability during the on-line operation.
For achieving expansion of functions with flexibility, it is enough that as the bus or route on which a new storage control unit is added is adopted an interface which is used for connecting with the host computer(s), that each storage control unit to be added further has it""s own cache memory, and that the control information of the logical unit (one logical drive or a group of plurality of logical drives) is copied into the above-mentioned cache memory as a logical unit of the storege devices.
According to the present invention, there is established a data storage system, in which a fiber channel standardized by ANSI X3T11 is applied to, for the host device(s), the storege device(s) such as the magnetic disk device and so on, and the storage control unit(s).
And, in said system, a new storage control unit is added onto the fiber channel network during on-line operation, so as to succeed or take over the control information from the existing storage control unit, thereby achieving load distribution between the storage control unit being newly added and the existing storage control unit.
The new storage control unit has a means of a function for obtaining (i.e., succeeding) the control information by a unit of the logical unit from the existing storage control unit on the fiber channel network through the fiber channel network, when being added to the existing fiber channel network during the on-line operation of the computer system. Upon completion of the obtaining or succeeding of the control information, it serves under the storage control unit, into which a predetermined logical unit is added.
The storage control unit being newly added to processes a command process request if it is issued from the host computer, for the logical unit which serves under the control of it. In this manner, the storage control unit being newly added to and the existing storage control unit share or distribute the load between them.
The load distribution according to the present invention can be applied even if a plurality of the existing storage control units on the fiber channel network have no means nor function of performing the load distribution and integration during the on-line operation. However, when putting the present invention into the embodiment, there is necessity to establish a function for conducting the succession of the control information.
Further, when succeeding or taking over the control information by the unit of logical unit, an operator establishes a means or a function of designating start for the succession of logical unit and the operation mode thereof during the operation of succession on the host computer or the storage control unit, by using management tool being operative on the host computer which is connected to a network, such as the fiber channel network, the LAN (Local Area Network) and so on, or by using a panel of the storage control unit, thereby enabling to perform the addition of the new storage control unit at an appropriate timing.
Further, in more details, the storage control unit which is newly connected to the fiber channel network has the means or function of succeeding the information for the purpose of identifying the storage control unit uniquely from the host computer, i.e., N_Port address, from the existing storage control unit which is connected to the fiber channel network and owns the logical unit to be succeeded, when performing the succession of the control information by the unit of the logical unit. Thereby, it is not necessary to change or alter the route of the command process request which is issued from the host computer.
The storage control unit according to the present invention has a control memory, and it has the means or function of memorizing the control information on said control memory, which is necessary for the succession of the logical unit and can be represented by, such as a physical drive control table, into which are stored the kinds of the magnetic disk device or the others, the memory capacities of the storage devices, the number of blocks, the condition of each storage device, the constructive information of RAID (Redundant Arrays of Inexpensive Disks), etc., and a logical unit control table, into which are stored header LBA (Logical Block Address) and last LBA of the logical unit.
And, the storage control unit which is newly added onto the same fiber channel network has a means or function of copying the above-mentioned control information, from the control memory on the storage control unit which has already been existing before on the above-mentioned fiber channel network to the control memory of the storage control unit which is newly added.
The above-mentioned control memory on the storage control unit may be of a volatile one, however is of a non-volatile memory, in general. Also, by writing the contents (i.e., established information on the control table or the others) into the storage device, such as the magnetic disk device or the others which is connected to the fiber channel network, it is possible to obtain the same effect as obtained when the control memory is made of the non-volatile memory. Namely, when occurring abrupt interruption in the electric power source, the storage control unit can maintain the established information permanently, until when performing the reset of that established information, for example.
Also, by using the succession of the control information by the unit of logical unit during the on-line operation, according to the present invention, it is also possible to integrate or gather several processes which are conducted by the plural storage control units into an arbitrary storage control unit.
In a method for adding a new storage control unit, (1) after connecting the new storage control unit to the fiber channel network physically, (2) a link set is issued from that storage control unit side to the fiber channel network, so as to perform logical log-in into the fiber channel network. (3) Thereafter, the operator conducts acknowledgment of the storage control unit(s) from the management tool on the host computer which is connected to the fiber channel network, or from a panel of the storage control unit, (4) setting or establishing a designation of the logical unit of which the storage control unit being newly added is in charge, an instruction of start of the succession of logical unit, and a manner of response when the process request is issued from the host computer to the storage control unit which has already been existing on the fiber channel network before, during the succession of that logical unit, and (5) the transfer of the control information of logical unit from the storage control unit which has already been existing on the fiber channel network before to the storage control unit which is newly added. (6) Further, in the storage control unit which has already been existing on that fiber channel network before, a plurality of the N_Port addresses, i.e., the information for identifying the storage control units uniquely from the host computer, are established, (7) and the storage control unit which is newly added to the fiber channel network succeeds or takes over a portion of the above-mentioned N_Port addresses, thereby rendering the change or alter of the route for the command process request unnecessary. (8) Further, the storage control unit, existing on the fiber channel network during the on-time operation of the computer system, succeeds or takes over the control information by a unit of the logical unit from the other storage control unit which is connected to the same fiber channel network, (9) so as to be in charge of the command process request being issued from the host device to that succeeding logical unit thereafter, (10) thereby achieving the load distribution between or among the storage control units existing on the fiber channel network. (11) Depending upon necessity, the integration of processes which are performed by the plurality of storage control units into an arbitrary storage control unit is performed by applying the technology of succeeding the control information of the logical unit during the on-line operation therein.